DOC questions

[Oregon Grown Reef]

I've been reading about dissolved organic carbon, but I'll be the first to admit that I have no idea what I'm reading. What is doc, is it bad or good, and are there nutrient removal methods that are bad because they lower/raise them? For example, @Garf said this in another thread:

I ran a scrubber for 2 years, concluded the dissolved organics contribute to a coral algae phase shift. Not doing one again.

Is there a side to this hobby that I've been completely unaware of? From what Garf is insinuating (if I'm understanding correctly) , doc will change the colors of your corals if in too low/high demand. Does it also affect mortality rate?

 

[unchaotic]

I'd just move along. Multiple people asked him to elaborate and he never did.

 

[Oregon Grown Reef]

I'd just move along. Multiple people asked him to elaborate and he never did.

The question isn't just posed to him, hence why I posted here. He's not even the first one that I saw say something like this. I'm honestly hoping @Randy Holmes-Farley will come in and dumb down the conversation to help me understand.

 

[DE FISH]

Watching……

 

[Garf]

There’s loads about DOC on the web, I first came across it during my algal derived insomnia, a long time ago now, here’s one;

Directory of Open Access Journals

DOAJ is a community-curated online directory that indexes and provides access to high quality, open access, peer-reviewed journals.

core.ac.uk

SUMMARY
The following collection of studies supports the idea that the microbial and macrobial community are strongly interrelated and subjected to positive feedback loops in which contribute to phase shifts from coral to algal dominance.
Microbes inhabiting coral surfaces are subjected to shifts in community composition and elevated activity in response to increased availability of algae derived DOM. This increased microbial activity, facilitated by bioavailable algae derived OM, has been identified as a key mechanism leading to coral mortality. First, Kuntz et al. (2005) and Kline et al. (2006) showed that elevated concentrations of organic compounds were more detrimental to coral health than increased availability of inorganic nutrients. Concurrently, Smith et al. (2006) conducted an empirical study which demonstrated that coral mortality was mediated by algal released dissolved compounds which induced microbe facilitated hypoxia. Supporting results have been provided by Barott et al. (2009) and a recent study by Morrow et al. (2012) who identified consistent patterns in physiology and microbial community differentiation across different types of coral-algal competitive interactions. Here turf- or macroalgae interactions with corals created a zone of hypoxia and altered pigmentation in the coral tissue. In the companion articles (Haas et al., 2010a; Haas et al., 2010b) we can provide the first direct visualization of oxygen gradients originating from corals and algae, as well as at the interfaces. The study shows 2 dimensional images of
Haas et al. (2013), PeerJ, DOI 10.7717/peerj.108 21/28
oxygen gradients over time in varying flow conditions and can thereby provide compelling evidence for the existence of hypoxic zones in coral-algae interaction processes. By using oxygen optodes as biological sensors, Gregg et al., 2013, revealed that in these processes the source of DOC, rather than the microbial community is the driving factor for microbial oxygen drawdown.
On a larger scale Dinsdale et al. (2008) described an increase of the microbial density by an order of magnitude from islands dominated by hermatypic corals and coralline algae towards islands dominated by fleshy macro- and turf algae. This study also demonstrated that on islands with high cover of fleshy macro- and turf algae the microbial community was dominated by heterotrophs, including a large percentage of potential pathogens. Adding to this, Nelson et al. (2013) showed that, in contrast to coral exudates, which facilitated high microbial diversity with few virulence factors, macroalgal exudates selected for less diverse communities heavily enriched in copiotrophic lineages, containing pathogens with increased virulence factors.

 

[Oregon Grown Reef]

There’s loads about DOC on the web, I first came across it during my algal derived insomnia, a long time ago now, here’s one;

Directory of Open Access Journals

DOAJ is a community-curated online directory that indexes and provides access to high quality, open access, peer-reviewed journals.

core.ac.uk

SUMMARY
The following collection of studies supports the idea that the microbial and macrobial community are strongly interrelated and subjected to positive feedback loops in which contribute to phase shifts from coral to algal dominance.
Microbes inhabiting coral surfaces are subjected to shifts in community composition and elevated activity in response to increased availability of algae derived DOM. This increased microbial activity, facilitated by bioavailable algae derived OM, has been identified as a key mechanism leading to coral mortality. First, Kuntz et al. (2005) and Kline et al. (2006) showed that elevated concentrations of organic compounds were more detrimental to coral health than increased availability of inorganic nutrients. Concurrently, Smith et al. (2006) conducted an empirical study which demonstrated that coral mortality was mediated by algal released dissolved compounds which induced microbe facilitated hypoxia. Supporting results have been provided by Barott et al. (2009) and a recent study by Morrow et al. (2012) who identified consistent patterns in physiology and microbial community differentiation across different types of coral-algal competitive interactions. Here turf- or macroalgae interactions with corals created a zone of hypoxia and altered pigmentation in the coral tissue. In the companion articles (Haas et al., 2010a; Haas et al., 2010b) we can provide the first direct visualization of oxygen gradients originating from corals and algae, as well as at the interfaces. The study shows 2 dimensional images of
Haas et al. (2013), PeerJ, DOI 10.7717/peerj.108 21/28
oxygen gradients over time in varying flow conditions and can thereby provide compelling evidence for the existence of hypoxic zones in coral-algae interaction processes. By using oxygen optodes as biological sensors, Gregg et al., 2013, revealed that in these processes the source of DOC, rather than the microbial community is the driving factor for microbial oxygen drawdown.
On a larger scale Dinsdale et al. (2008) described an increase of the microbial density by an order of magnitude from islands dominated by hermatypic corals and coralline algae towards islands dominated by fleshy macro- and turf algae. This study also demonstrated that on islands with high cover of fleshy macro- and turf algae the microbial community was dominated by heterotrophs, including a large percentage of potential pathogens. Adding to this, Nelson et al. (2013) showed that, in contrast to coral exudates, which facilitated high microbial diversity with few virulence factors, macroalgal exudates selected for less diverse communities heavily enriched in copiotrophic lineages, containing pathogens with increased virulence factors.

This is interesting. The doc released from the algae can cause higher rates of mortality? Mind blowing. Why is it that refugiums and other algae based nutrient export methods are so popular? It's better to run higher nutrients than to have low nutrients and chaeto. This is just not something you really hear or see. It seems water changes and a good skimmer keep them in check. Does activated carbon work as well?

 

[Dan_P]

I've been reading about dissolved organic carbon, but I'll be the first to admit that I have no idea what I'm reading. What is doc, is it bad or good, and are there nutrient removal methods that are bad because they lower/raise them? For example, @Garf said this in another thread:

Is there a side to this hobby that I've been completely unaware of? From what Garf is insinuating (if I'm understanding correctly) , doc will change the colors of your corals if in too low/high demand. Does it also affect mortality rate?

I can’t address the effect on coral.

Dissolved organic carbon measures many, many things and may not be a very useful metric. Triton’s NDOC test measures TOC, total organic carbon, which is DOC+POC (particulate organic carbon). Skimmers remove some DOC and some POC, granular activated carbon also removes some DOC. Aquariums tend to have more TOC than reefs and the ocean, but I am not sure the hobby has come to consensus on a “good” level. I think it comes back to not knowing what makes up DOC and whether what makes up DOC is wildly different among aquariums.

A side note. Nutritious DOC probably gets consumed rather quickly by bacteria. Maybe the stuff hanging around and being measured is useless junk that does nothing more than color aquarium the water yellow. Coral might not care about it,

 

[Randy Holmes-Farley]

I generally wouldn't lump DOC as a single thing.

It's like asking if a bucket of rocks is valuable. Diamonds? Gold? Very valuable rocks. Sandstone? not so much. Enriched uranium? Maybe good if you do not stand near it. lol

I discuss organics in substantial detail here:

Organic Compounds in the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com